This application claims the benefit of priority to Japanese Patent Application Nos. 2004-149842 filed on May 20, 2004 and 2004-377393 filed on Dec. 27, 2004, both herein incorporated by reference.
1. Field of the Invention
The present invention relates to a perpendicular magnetic recording head which performs recording by applying a vertical magnetic field to a recording medium, such as a disk having a hard surface, and more particularly, to a perpendicular magnetic recording head capable of suppressing the generation of fringing on a recording pattern and improving recording efficiency.
2. Description of the Related Art
A perpendicular magnetic recording head has been used for a vertical magnetic recording system to record magnetic data on a recording medium, such as a disk, with high density. In general, this perpendicular magnetic recording head has the structure that it has an auxiliary magnetic pole layer made of ferromagnetic materials, and a main magnetic pole layer which is made of ferromagnetic materials and which is formed with a gap from the auxiliary magnetic pole layer.
A front end of the auxiliary magnetic pole layer and a front end of the main magnetic pole layer are shown on a medium-opposing surface of a recording medium, and they are magnetically connected to each other at the rear side of a height direction. A coil layer is formed between the auxiliary magnetic pole layer and the main magnetic pole layer. When a recording magnetic field is induced in the auxiliary magnetic pole layer and the auxiliary magnetic pole layer by supplying electricity to the coil layer, on the medium-opposing surface of the recording medium, a leakage recording magnetic field is generated between the auxiliary magnetic pole layer and the main magnetic pole layer. The leakage recording magnetic field passes through the recording medium, so that recording signals are recorded on the recording medium.
Here, the ferromagnetic material used for the main magnetic pole layer has high saturation magnetic flux density. However, since the ferromagnetic material has low permeability in general, it is difficult to induce the recording magnetic field induced in the main magnetic pole layer in the front end of the main magnetic pole layer. For this reason, there is provided a perpendicular magnetic recording medium in which a yoke layer made of materials having high permeability is adjacently formed to the main magnetic pole layer and it is intended to induce the recording magnetic field in the front end of the main magnetic pole easily.
In this way, in the perpendicular magnetic recording head where the yoke layer is formed, it is effective to make the yoke layer approach the medium-opposing surface of the recording medium in effectively inducing the recording magnetic field in the front end of the main magnetic pole. However, if the yoke layer approaches the medium-opposing surface of the recording medium too much, it becomes easy for the recording magnetic field to flow into the recording medium from a front end of the yoke layer as well. As a result, there is a problem in that a so-called side fringing occurs.
As the perpendicular magnetic recording head capable of suppressing the side fringing problem, Japanese Unexamined Patent Application Publication No. 2002-197615 (see FIGS. 1 and 10 or FIGS. 3 and 14) has proposed a perpendicular magnetic recording head, in which a front end surface 35a of a yoke layer is formed into an inclined surface or a curved surface so as to approach the medium-opposing surface of the recording medium toward a top surface from a bottom surface.
In the perpendicular magnetic recording head disclosed in Japanese Unexamined Patent Application Publication No. 2002-197615, since the yoke layer 35 made of materials having high permeability is formed in contact with the main magnetic pole layer 24, the recording magnetic field can be induced in the front end of the main magnetic pole layer 24. At the same time, since the front end surface 35a of the yoke layer 35 is formed into an inclined surface and a cross-sectional area decreases, a magnetic volume of the yoke layer 35 in the vicinity of the medium-opposing surface of the recording medium is suppressed. Therefore, the recording magnetic field can be restrained from flowing into the recording medium from the front end surface of the yoke layer 35, so that the side fringing can be suppressed.
However, in the perpendicular magnetic recording head disclosed in Japanese Unexamined Patent Application Publication No. 2002-197615, a width at an area where the front end surface 35a of the yoke layer 35 is formed increases continuously as going in the height direction, but the width is constant at locations more progressed than the front end surface 35a in the height direction. In addition, whether the width is constant from a top surface of the yoke layer 35 to a bottom surface of the yoke layer 35 is not plainly described. In addition, from FIGS. 1 and 10, in an area where a film thickness of the front end surface of the yoke layer 35 is changed (inclined), whether a width changes in accordance with the thickness is not plainly described.
Therefore, in the yoke layer 35 disclosed in Japanese Unexamined Patent Application Publication No. 2002-197615, since there is a limitation in increasing the magnetic volume as a whole, it is not possible to induce the recording magnetic field effectively in the main magnetic pole layer 24.